I think I might have a similar problem with my Fairphone 5. Today, I received a call, after which I couldn't turn the screen off anymore. The phone wouldn't respond to the power button. I wasn't too bothered by this since I needed to send a message after the call, so I continued using the phone.
I started up Waydroid to send the message. After that, I tried to force reboot the phone since the power menu didn't pop up. Unfortunately, the phone booted to a black screen. I could still hear the screenshot sound, though. Now this happens every time, and I can't see anything on the screen. Touch inputs are recognized, and I briefly see the screen lighting up when I run:
sudo systemctl restart repowerd
However, it doesn't turn the screen back on. I've also tried reinstalling Ubuntu Touch (stable, RC, and daily channels, even 24.04-2.x/daily), but that hasn't made a difference either. I'm aware that a full wipe (including userdata) could help, but I'd prefer to explore other solutions first if possible. Any help is appreciated!